Intervalometer



L. L. KIELMAN INTERVALOMETER vJan. 28, 1958 Filed April '12. 195

2 Sheets-Sheet 2 INVENTOR. KIELMAN LEO L. BYf

7 ATTORNEYS United States Patent 2,821,583 INTERVALOMETER Leo L. Kielman, China Lake, Califi, assignor to the United States of America as represented by the Secretary of the Navy Application April 12, 1956, Serial No. 577,900 6 Claims. (Cl. 200-24) (Granted under Title 35, U. S. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the pay ment of any royalties thereon or therefor.

The present invention relates to electrical switches and particularly to a mechanically operated intervalometer.

Heretofore, cascade resistance type and motor driven commutator type intervalometers have been used. The cascade resistance type intervalometer usually comprised a series of contacts, each contact being placed on a long narrow strip of thin metal. Each metal strip was fastened rigidly at one end, while the contact bearing end of each strip was held off its opposing contact by means of a small resistance wire. Current was made to flow through the resistance Wire, which in a short interval of time caused the wire to part and allowed the strip contact to close the circuit with its lower contact. The procedure also allowed the current to flow to the next strip contact and thus repeated itself in parting the resistance wire and closing the successive circuits. The motor driven commutator type intervalometer used an electric motor to drive a commutator, and used brushes spaced radially around and bearing upon the commutator to pick off the desired intervals. The cascade resistance type intervalometer has the disadvantage of being too large, has too much contact bounce upon closure, and requires too delicate an adjustment of the resistance wire. Likewise, the disadvantages of the cascade resistance type intervalometer are that it is expensive and requires external power to drive the unit.

The present invention avoids the disadvantages associated with these prior type intervalometers by providing a spring wound mechanically operated intervalometer which has no delicate adjustments, and is relatively small and inexpensive.

In accordance with the foregoing, it is an object of the present invention to provide an intervalometer in which the time intervals may be varied easily, and which con tains a self powered drive mechanism.

Another object of the invention is to provide a mechanically operated spring wound intervalometer in which only one circuit is closed at any one time.

A further object of the invention is to provide an improved mechanical intervalometer having adjustable driving torque and which is small and inexpensive.

Other objects and many of the attendant advantages of the present invention will become apparent as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a cross sectional view taken along the axis of the intervalometer;

Fig. 2 is a perspective view of the intervalometer drum and contact shoe;

. Fig. 3 is a perspective view of the intervalometer.

Referring now to the drawings wherein like numerals refer to like parts throughout each of the figures, the construction of the spring-wound, helical-track intervalometer of the present invention is as follows: A cylindrical tube section 10, made from an insulating material such as Lucite or the like, is inscribed on its inside diameter with a helical track 12; this is illustrated in Fig. 1. One

2,821,583 Patented Jan. 28, 1958 having a bearing 15 at its center. Bearing 15 as well as the other bearings used in the intervalometer may be made of a graphitic material to decrease friction and eliminate the need for further lubrication. A metal cylinder 16, Fig. 2, of aluminum or magnesium alloy or the like and which may be hollow to reduce its mass, is provided with a slot 18 running axially along its face and a bore 19 to accommodate drive shaft 20. The cylinder and drive shaft assembly are fitted into tube section 10, Fig. 1, by passing the drive shaft 20 through bearing 15 in bearing plate 14 and allowing cylinder 16 to bear against raised portion 17 of bearing plate 14. Additional shaft support is provided by hearing 23 and bearing plate 22 which is fitted on the other end of tube 10. Bearing plate 22 has collector 24 and collector terminal 26 mounted thereon as means for providing electrical contact with metal cylinder 16.

A small collector shoe 28, of brass for example, slides in slot 18 on cylinder 16. The upper portion 29 of collector shoe 28 is fashioned to fit the contour of the helical track 12 on the inside of tube 10. Collector shoe 28 is fitted so that a minimum of friction exists when shaft 20 is rotated and collector shoe 28 follows the inscribed track 12.

Electrical contacts 30 are mounted on tube 10 so that one end is located in track 12, protruding slightly into and contoured to the shape of the track groove. Contacts 30 are mounted so as to contact portion 29 of collector shoe 28 with a small amount of positive pressure, thereby providing good electrical contact. A contact terminal 32 is connected to each of contacts 30, and is mounted on the outside of tube 10.

The motive power to turn drive shaft 20 and cylinder 16 comprises a helical spring 34 having one end anchored to drive shaft 20 by means of a screw 36, or the like. Leaf spring 38 is used at the anchor point of main spring 34 and serves to prevent failure of the main spring at that point upon repeated reversal. A housing for spring 34 is provided by an additional tube section 40 having one end thereof fitted to hearing plate 14, and the other end fitted with bearing plate 42 having a bearing 43 to accommodate drive shaft 20. Tubes 10 and 40, and bearing plates 14, 22 and 42 comprise the intervalometer housing. A small slot 44 is provided in tube 40; the other end of main spring 34 is brought up through slot 44 and securely fastened onto tube 40 with a screw 45. In order to allow for slight misalignment and a means for anchoring tubes 10 and 40 to the center bearing plate 14, a plurality of set screws, such as 46 and 47, are used to hold the tubes rigidly to the center bearing plate.

A ratchet arrangement is fitted to the end of the drive shaft 20 and bearing plate 42, to facilitate winding the mechanism to a desired degree, and also to provide some method of holding the spring 34 in the wound state and for releasing it. The ratchet consists of a small pinion gear 50 fitted with a winding knob 52 and mounted on the end of shaft 20. Pawl 54 for engaging pinion gear 50 is mounted on pivot 56 onto the side of bearing plate 42. A small spring 57 exerts pressure on pawl 54 and thus serves to keep the mechanism in the wound state. Release of the spring 34 is accomplished by simply exerting pressure on the end of pawl 54, thus disengaging the pawl from pinion gear 50 and allowing spring 34 to unwind and drive the cylinder contact device. By increasing or decreasing the length of helical track 12 inscribed in tube 10, longer or shorter time intervals can be obtained. Long or short time intervals can also be obtained by varying spring tension or by varying contact spacing along the helical track.

I Qperation of the spring wound helical track intervalomg racemes eter of the present invention is accomplished simply by winding the spring 34, by means of winding knob 52, until the collector shoe 28 reaches its limit of travel in cylinder slot 18. When this limit is reached, a definite resistance is felt when effort is applied to the winding knob. At this point the spring loaded pawl 54 engages the pinion gear 50 and holds the spring 34 in the Wound state. Release of spring 34 allows drive shaft 20 to rotate and drive collector shoe 28 along the internally inscribed helix 12. As the collector shoe travels along the helix track it makes contact with contacts 30 that protrude into the raceway.

Current flow through the device begins at collector terminal 26, from which it flowsthroughcollector 24 into cylinder 16 and to collector shoe 28. As collector shoe 28 strikes a contact 30 the circuit is completed, and the current flow continues through the engaged contact, on through contact terminal 32, through the external circuitry and back to the primary source.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. An intervalometer comprising a hollow cylindrical housing of electrically insulating material, a shaft supported for rotation along the axis of the housing, a-drum of electrically conductive material fixed to one end of the shaft in coaxial relationship thereto, a straight track formed in and extending axially of the drum, a helical groove formed in the inner wall of the housing, a single collector shoe slidable in said track and having a-portion guided in said groove, a plurality of contacts longitudinally spaced along said groove, a contactor slidably engaging said drum, and a self-powered drive means for rotating said shaft and drum, the arrangement being that rotation of the drum causes said shoe portion to traverse said groove whereby to sequentially engage said contacts and sequentially complete the circuits between said contactor. and contacts.

2. An intervalometer comprising a hollow cylindrical housing of electrically insulating material, a shaft supported on hearing ,plates in said housing for rotation along the axis of the housing, a drum of electrically con ductive material fixed to said shaft in coaxial relationship thereto, a straight track formed in and extending axially of saiddrum, a helical grooveformed in the inner Wall of said housing, a single collector shoe slidable in saidtrack and having a raised portion guided in said groove, a plurality of contacts longitudinally spaced along and protruding slightly into said groove, an electrical terminal for each of said contacts mounted on the out side of said housing, a contactor slidably engaging said drum, an electrical terminal for said contactor mounted on the outside of said housing, and a self-powered. drive means for rotating said. shaft and drum, the arrangement beingthat-rotation of the drum causes said shoe portion to traverse said groove whereby said raised shoe portion will sequentially engage said contacts and sequentially complete the circuits between said-contactor terminal and said contact terminals.

3. An intervalornetercomprising a hollow cylindrical housing of electrically insulating material, a shaft supported for rotation along the axis of the housing, a drum of electrically conductivematerial fixed to said shaft in coaxial relationship thereto, a straight track'formed in and-extending axiallyof said drum, a helical groove formed in the innerwall of said housing, a single collector shoe slidable in said track and having a portion guided in said groove, a contactor slidably engaging said drum, and drive means for rotating said shaft and a selfpowered drive drum, said drive means consisting of a spring having one end anchored to said shaft and the other end anchored to said housing, the arrangement being that rotation of said drum causes said shoe portion to traverse said groove whereby to sequentially engage said contacts and sequentially complete the circuits between said contactor and contacts.

4. An intervalometer comprising. a hollow cylindrical housing of electrically insulating material, a shaft supported for rotation along the axis of said housing, spring means for driving'said shaft in rotation, said spring means having one end fastened to said drive shaft and its other end fastened to said housing, a drum of electrically conductive material fixed to said shaft in coaxial relationship thereto, a straight track formed in and extending axially of said drum, a helical groove formed in the inner wall of said housing, a single collector shoe slidaole in said, track and having a portion guided in said helical groove, a. plurality of contacts longitudinally spaced along saidgroove, a contactor slidably engaging said drum, .a holding pinion gear mounted on said shaft and a pinion release means mounted on said housing for preventing said shaft from rotating until released, the arrangement being that rotation of said drum causes said shoe portion to traverse said groove whereby to sequentially engage said contacts and sequentially complete the circuits between said contactor and said contacts.

5. Anintervalometer comprising a hollow cylindrical housing of electrically insulating material, a shaft supported for rotation along the axis of said housing, selfposgered means for driving said shaft in rotation, means for preventing said shaft. from rotating until released, a n of electrically conductive material fixed to said shaft in oaxial relationshipthereto, a'straight track formed in and extending axially of said drum, a helical groove formed in the inner wall of said housing, a single collector shoe slidable .in said track and having a portion guided in said groove, a plurality of contacts longitudinally spaced along said helical groove, and a contactor slidably engaging said drum the arrangement being that rotation of said drum causes said shoe portionto traverse said groove whereby to sequentially engage said contacts and sequentially complete the circuits between said contactor and said contacts.

6. An intervalometer comprising a hollow cylindrical housing of electrically insulatingmaterial, a drive shaft supported on bearing plates in said housing for rotation along the axis of said housing, a drum of electrically conductive material fixed to said shaft in coaxial relationship thereto, a straight trackformed in and extending axially of said drum, a helical groove formed in the inner wall or" saidhousing, a single collector shoe slidable in said track and having a raised portion guided in said helical groove, a plurality of contacts longitudinally spaced along and protruding slightly intosaid helical groove, an electrical terminal for each of said contacts mounted on the outside of said housing, a contactor slidably engaging said drum, an electrical terminal for said contactor mounted on; theoutside of, said housing, spring means for driving said shaftand drum in rotation, said spring means having one end fastened to said shaft and its otherend fastened to said' housing, and means for preventing said shaft fromrotating until released, said shaft rotation prevention means consisting of a holding pinion gear mounted on said drive shaft and a pinion release means mounted on said housing, the arrangement being that ro-' tation of said drum causes said shoe portion to traverse said helical groove whereby said raised shoe portion will sequentially engage said, contacts and sequentially complaifi the circuits between said contactor and said contacts.

Referenges qited in the file of this patent UNITED STATES PATENTS !,6i)6,l53 Douglas Nov. 9, 1226 2,406,628 Meyers Aug. 20, 1946 2,472,230 Reimschmidt June 7, 1949 

